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To: Dave Jones <davej@redhat.com>
Cc: Zachary Amsden <zach@vmware.com>, Pavel Machek <pavel@ucw.cz>,
       Andrew Morton <akpm@osdl.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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       Ingo Molnar <mingo@elte.hu>, torvalds@osdl.org
Subject: Re: [PATCH 1/10] Cr4 is valid on some 486s
References: <200511100032.jAA0WgUq027712@zach-dev.vmware.com>
	<20051111103605.GC27805@elf.ucw.cz> <4374F2D5.7010106@vmware.com>
	<Pine.LNX.4.64.0511111147390.4627@g5.osdl.org>
	<4374FB89.6000304@vmware.com>
	<Pine.LNX.4.64.0511111218110.4627@g5.osdl.org>
	<20051113074241.GA29796@redhat.com>
From: Andi Kleen <ak@suse.de>
Date: 13 Nov 2005 11:59:55 +0100
In-Reply-To: <20051113074241.GA29796@redhat.com>
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Dave Jones <davej@redhat.com> writes:
> 
> Looks like the Ubuntu people already did this...
> 
> http://www.kernel.org/git/?p=linux/kernel/git/bcollins/ubuntu-2.6.git;a=commitdiff;h=048985336e32efe665cddd348e92e4a4a5351415;hp=1cb630c2b5aaad7cedaa78aa135e6cecf5ab91ac

It's probably not needed. At least AMD K7/K8 has a SYSCFG MSR bit to
do this (or rather they disable bus cycles for locks that makes them
very cheap) Intel has one too in a different MSR that looks similar.
With some luck they're even already set by the BIOS on UP systems.  I
know they are on some AMD systems.

But overall the feature doesn't help longer term because single
threaded CPUs are on their way out.

-Andi
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